Perleididae is a group of stem neopterygian fishes known only from the Triassic. Here, we report the discovery of a new perleidid, Teffichthys wui sp. nov., based on six well-preserved specimens from the late Smithian (Olenekian, Early Triassic) marine deposits of Jurong, Jiangsu and Chaohu, Anhui, China. This new discovery documents the third and youngest species of Teffichthys, which is slightly younger than the Dienerian (Induan) T. elegans from Guizhou and the early Smithian T. madagascariensis from Madagascar. The new species shows diagnostic features of Teffichthys (presence of a spiracular, 38–41 lateral line scales, and no more than three epaxial rays in the caudal fin) but differs from T. madagascariensis and T. elegans in some autapomorphies (e.g., a horizontal opercle/subopercle contact and smooth scales with a nearly straight posterior margin). The diagnostic features for the genus Teffichthys and the family Perleididae are emended based on detailed comparisons of the new taxon with other perleidids. The phylogenetic relationships of perleidids with other stem neopterygians are discussed using a cladistic approach, and the results provide new insights into the phylogeny and classification of main stem neopterygian clades.